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[Merged by Bors] - move system_param fetch struct into anonymous scope to avoid name collisions #4100

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[Merged by Bors] - move system_param fetch struct into anonymous scope to avoid name collisions #4100

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55cba37
rename system_param fetch struct
robtfm Mar 4, 2022
2053aa0
anonymous scope for fetch struct
robtfm Mar 4, 2022
b68ae8d
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robtfm Mar 5, 2022
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70 changes: 37 additions & 33 deletions crates/bevy_ecs/macros/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -366,51 +366,55 @@ pub fn derive_system_param(input: TokenStream) -> TokenStream {
}));

let struct_name = &ast.ident;
let fetch_struct_name = Ident::new(&format!("{}State", struct_name), Span::call_site());
let fetch_struct_visibility = &ast.vis;

TokenStream::from(quote! {
impl #impl_generics #path::system::SystemParam for #struct_name #ty_generics #where_clause {
type Fetch = #fetch_struct_name <(#(<#field_types as #path::system::SystemParam>::Fetch,)*), #punctuated_generic_idents>;
}
// We define the FetchState struct in an anonymous scope to avoid polluting the user namespace.
// The struct can still be accessed via SystemParam::Fetch, e.g. EventReaderState can be accessed via
// <EventReader<'static, 'static, T> as SystemParam>::Fetch
const _: () = {
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impl #impl_generics #path::system::SystemParam for #struct_name #ty_generics #where_clause {
type Fetch = FetchState <(#(<#field_types as #path::system::SystemParam>::Fetch,)*), #punctuated_generic_idents>;
}

#[doc(hidden)]
#fetch_struct_visibility struct #fetch_struct_name<TSystemParamState, #punctuated_generic_idents> {
state: TSystemParamState,
marker: std::marker::PhantomData<fn()->(#punctuated_generic_idents)>
}
#[doc(hidden)]
#fetch_struct_visibility struct FetchState <TSystemParamState, #punctuated_generic_idents> {
state: TSystemParamState,
marker: std::marker::PhantomData<fn()->(#punctuated_generic_idents)>
}

unsafe impl<TSystemParamState: #path::system::SystemParamState, #punctuated_generics> #path::system::SystemParamState for #fetch_struct_name<TSystemParamState, #punctuated_generic_idents> #where_clause {
fn init(world: &mut #path::world::World, system_meta: &mut #path::system::SystemMeta) -> Self {
Self {
state: TSystemParamState::init(world, system_meta),
marker: std::marker::PhantomData,
unsafe impl<TSystemParamState: #path::system::SystemParamState, #punctuated_generics> #path::system::SystemParamState for FetchState <TSystemParamState, #punctuated_generic_idents> #where_clause {
fn init(world: &mut #path::world::World, system_meta: &mut #path::system::SystemMeta) -> Self {
Self {
state: TSystemParamState::init(world, system_meta),
marker: std::marker::PhantomData,
}
}
}

fn new_archetype(&mut self, archetype: &#path::archetype::Archetype, system_meta: &mut #path::system::SystemMeta) {
self.state.new_archetype(archetype, system_meta)
}
fn new_archetype(&mut self, archetype: &#path::archetype::Archetype, system_meta: &mut #path::system::SystemMeta) {
self.state.new_archetype(archetype, system_meta)
}

fn apply(&mut self, world: &mut #path::world::World) {
self.state.apply(world)
fn apply(&mut self, world: &mut #path::world::World) {
self.state.apply(world)
}
}
}

impl #impl_generics #path::system::SystemParamFetch<'w, 's> for #fetch_struct_name <(#(<#field_types as #path::system::SystemParam>::Fetch,)*), #punctuated_generic_idents> #where_clause {
type Item = #struct_name #ty_generics;
unsafe fn get_param(
state: &'s mut Self,
system_meta: &#path::system::SystemMeta,
world: &'w #path::world::World,
change_tick: u32,
) -> Self::Item {
#struct_name {
#(#fields: <<#field_types as #path::system::SystemParam>::Fetch as #path::system::SystemParamFetch>::get_param(&mut state.state.#field_indices, system_meta, world, change_tick),)*
#(#ignored_fields: <#ignored_field_types>::default(),)*
impl #impl_generics #path::system::SystemParamFetch<'w, 's> for FetchState <(#(<#field_types as #path::system::SystemParam>::Fetch,)*), #punctuated_generic_idents> #where_clause {
type Item = #struct_name #ty_generics;
unsafe fn get_param(
state: &'s mut Self,
system_meta: &#path::system::SystemMeta,
world: &'w #path::world::World,
change_tick: u32,
) -> Self::Item {
#struct_name {
#(#fields: <<#field_types as #path::system::SystemParam>::Fetch as #path::system::SystemParamFetch>::get_param(&mut state.state.#field_indices, system_meta, world, change_tick),)*
#(#ignored_fields: <#ignored_field_types>::default(),)*
}
}
}
}
};
})
}

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